I got a few more issues.
I create manually the default storage pool and configure the default LXD profile to use it.
I launched a container, and it started successfully according to lxc list. Got an IP address.
But when I lxc exec mycontainer -- /bin/sh, this command gets stuck.
There is not output, and does not respond to Ctrl+C either. I can only kill -9 the process from another terminal.
I can stop the container. But when I try to delete it, I get the following.
Error: Error deleting storage volume: Failed to run: zfs destroy -r rpool/LXD/containers/mycontainer: cannot destroy 'rpool/LXD/containers/mycontainer': dataset is busy
The logs did not show something interesting, apart from /var/snap/lxd/common/lxd/logs/mycontainer/lxc.log:
lxc mycontainer 20200327025357.268 ERROR cgfsng - cgroups/cgfsng.c:mkdir_eexist_on_last:1136 - File exists - Failed to create directory "/sys/fs/cgroup/cpuset//lxc.monitor.mycontainer"
lxc mycontainer 20200327025357.269 ERROR cgfsng - cgroups/cgfsng.c:mkdir_eexist_on_last:1136 - File exists - Failed to create directory "/sys/fs/cgroup/cpuset//lxc.payload.mycontainer"
lxc mycontainer 20200327025357.274 WARN cgfsng - cgroups/cgfsng.c:fchowmodat:1448 - No such file or directory - Failed to fchownat(17, memory.oom.group, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )